Highly efficient and selective synthesis of dibutyl carbonate via the synergistic dual activation catalysis of tetraethylammonium prolinate ionic liquids

• [N2222][Pro] was employed for the phosgene-free synthesis of DBC.
• DBC was produced in nearly 72% yield under optimum conditions.
• High DBC yield originates from the synergistic catalysis of [N2222][Pro].

A facile, highly efficient and phosgene-free synthesis process of dimethyl carbonate (DMC) with n-butanol (BuOH) to dibutyl carbonate (DBC) by transesterification reaction has been studied in detail using tetraethylammonium-based amino acid ionic liquids ([N2222][AA]) as homogeneous catalysts. The results indicated that tetraethylammonium prolinate ([N2222][Pro]) exhibited the best catalytic activity in compared to other four [N2222][AA], and DBC could be obtained at a yield of 72% under optimum conditions. Furthermore, quantum-mechanical calculations manifested that such high DBC yield originated from the synergistic dual activation catalysis of [N2222][Pro]. [N2222][Pro] could activate BuOH and DMC well at the same time, which enhances the electrophilicity of BuOH and the nucleophilicity of DMC respectively, leading to the excellence catalytic performance.

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